Method for detecting roller bit bearing failure

ABSTRACT

A method for detecting failure of bearings in roller drill bits used in rotary drilling. Two drilling parameters-rotary torque and drilling rate-are measured and plotted with a third parameter ( psi ) equals ratio of the parameter of rotary torque divided by the parameter of drilling rate. A sharp increase in the third parameter psi indicates bearing failure.

Ullllcu DlalcD .l aecue Inventor Farrile S. Young, Jr.

Houston, Tex. Appl. No. 824,497 Filed May 14, 1969 Patented June 1, 1971 Assignee Esso Production Research Company METHOD FOR DETECTING ROLLER BIT BEARING FAILURE [56] References Cited UNITED STATES PATENTS 3,298,226 1/1967 Hildebrandt 73/151 3,324,717 6/1967 Brooks etal... 73/152 3,345,867 10/1967 Arps 73/151 Primary Examiner.lerry W. Myracle Att0rneys-Th0mas B. McCulloch, Melvin F. F incke, John S.

Schneider, Sylvester W. Brock, Jr., Kurt S. Myers and Timothy L. Burgess ABSTRACT: A method for detecting failure of bearings in roller drill bits used in rotary drilling. Two drilling parameters- --rotary torque and drilling rate-are measured and plotted with a third parameter (d1) equals ratio of the parameter of rotary torque divided by the parameter of drilling rate. A sharp increase in the third parameter \pindicates bearing failure.

TAKE-UP REEL 55 PENETRATION RATE SIGNAL I 7 Claims, 1 Drawing Fig.

[1.5. CI 73/151, 175/39 Int. Cl E21b 45/00 Field of Search 175/39, 50; 73/15l,151.5,152,136

SWlVEL PATENIED JUN 1 I97! 33 L TAKE-UP REEL DIVIDER W PENETRATION RATE SIGNAL P. R RATIO TORQUE SIGNAL CHART DRIVE INVIiN'IHR. FARRILE S. YOUNG,JR.,

ATTORNEY.

ROLLER BIT METHOD FOR DETECTING ROLLER BIT BEARING FAILURE FIELD OF THE INVENTION Background of the Invention When drilling boreholes with rotary well-drilling rigs, the time to roller bit bearing failure is difficult to predict. In the drilling of nonabrasive formations, the achievement of minimum drilling cost per foot is obtained by maximizing hours of rotation of the drill bit. The. prediction of bit bearing failure is, therefore,'critical since under such conditions, drill bits are totally consumed as a result of bit bearing failures.

It has been observed that drill pipe torque increases rapidly upon cone lockup. However, other drilling conditions such as hole deviation and gauge may give rise to premature high values of torque which can be misinterpreted. By observing the response of both torque and drilling rate during the life of the drill bit, it is possible to distinguish between bit bearing failure and other spurious torque responses.

SUMMARY or THE INVENTION Briefly, the invention concerns use of two drilling parameters, (l) rotary torque or torsional stress in the drill string and (2) drilling rate or rate of penetration of the drill bit to evaluate bit bearing failure. The method involves determining a third parameter q T/R; where T rotary torque and R penetration rate of the drill bit. At bit bearing failure, T increases, but R decreases, thereby defining a uniquely high value of ll.

BRIEF DESCRIPTION OF THE DRAWING The sole FIG. is a schematic illustration of a system capable of performingthe method of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the FIGURE, there is shown a well '10 that penetrates subsurface hydrocarbon-containing formation 11. Well has a surface casing 13 installed and cemented in place in accordance with conventional procedures. The well is drilled by means of a conventional rotary drill bit 15 rotated by means of a drill string 16 which extends to the surface where it passes through a conventional wellhead 18 that includes suitable blowout preventers and other equipment well known to those skilled in the art of rotary well drilling. Drill string 16 is rotated by a rotary table 20. The upper end of drill string I6 is connected by a swivel 21 and hooks 22 to a traveling block 23 supported from a stationary crown block 24 mounted on table 25. A cable or follow-line 30 connected at one end to traveling block 23 extends over pulley 31 to a takeup reel 32, both supported from table 25 along with an optical tachometer 33 moveable by cable 30 and capable of generating an electrical signal proportional to rate of rotation of tachometer 33.

Rotary drive motors 40 drive rotary 29 through the belt and shaft transmission generally designated 41. Low resistant shunts are placed in series with generators 42 which supply power to rotary drive motors 40. Low voltage signals are developed by the current passing through these shunts. These signals are amplified and calibrated so that the measurement of voltage drop across the shunt becomes proportional to the torsional stress in the drill pipe. The signals proportional to the torsional stress are sent along line 45 to a pen operator 46 connected to a pen 47 mounted on a chart 58, rotated by a drive 49. Signals indicative of the torque are also sent to an electronic divider means 50, e.g., an operational amplifier. The electrical signals proportional to rate of penetration resulting from movement of cable 30 downwardly in response to movement of block 23 are transmitted along line 55 to a pen operator 56 connected to a pen 57 mounted on chart 48. Signals indicative of rateof penetration are also transmitted to divider means 50 which functions to divide the torque by the rate of chart 48. Thus, line 63 on chart 48 indicates torque; line 64 on chart 48 indicates rate of penetration of the drill bit; and line 65 on chart 48 indicates ill, the relation of torque divided by rate of penetration.

In operation, as indicated in the drawing, the ratio of torque divided by penetration rate is essentially constant throughout the life of the drill bit up to the point of bearing failure. As the hard metal surfaces on the roller race spall, torque increases as a result of the cone lockup and the rate of penetration is reduced. There could be several reasons for a reduction in penetration rate, but when a cone locks, efficiency of the drilling mechanism is reduced by one-third. ln soft formations, when torque increases, penetration rate normally increases also, but at a slower rate, Conversely, in harder formations, such as dense shale, where penetration rate is slower, torque is reduced but, again, disproportionately. Accordingly, the ratio of torque divided by penetration rate remains constant up to the point of bearing failure. As indicated at 66 on the chart, a substantial increase in ii: indicates bearing lock.

Field practice will result in defining a maximum value of ill. The parameter ml: may be computed by means of an analog or digital computer programmed for solution using feedback values of torque and drilling rate. It also may be conveniently displayed or recorded for observation.

Other techniques are available for obtaining signals-electrical or pneumatic-proportional to torsional stress in the drill pipe and rate of penetration other than those illustrated and described above. Thus, another method for obtaining electrical signals proportional to torsional stress is shown and described in US. Pat. No. 3,298,226, issued to Hildebrandt, Jan. 17, 1967, entitled, System for Recording Work Done During Rotary Drilling Operations. In this method, a loadcell device measures the stress in the chain which drives the rotary table and also generates a signal calibrated in terms of rotary torque. A third technique uses an electronic device installed on the drilling equipment, shown and described in US. Pat. No. 3,295,367, issued to Rundell, Jan. 3, 1967, entitled, Sensitive Torque Meter."

Having fully described the objects, advantages, apparatus and operation of my invention, 1 claim:

I. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising:

measuring and displaying the ratio parameter ii: of the parameter of rotary torque in said drill string divided by the parameter of penetration rate of said drill bit through said earth formations when drilling said borehole.

2. A method as recited in claim 1 including displaying also said parameter of rotary torque and said parameter of penetration rate.

3. A method as recited in claim 2 including plotting on a chart said ratio parameter iii.

4. A method as recited in claim 3 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.

5. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string whendrilling boreholes through earth formations comprising:

measuring parameters of rotary torque in said drill string and penetration rate of said drill bit through said earth fonnations when drilling a borehole; and

obtaining the ratio parameter lb of said parameter of rotary torque divided by said parameter of penetration rate.

6. A method as recited in claim 5 including plotting on a chart said ratio parameter 11.

7. A method as recited in claim 6 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate. 

1. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising: measuring and displaying the ratio parameter psi of the parameter of rotary torque in said drill string divided by the parameter of penetration rate of said drill bit through said earth formations when drilling said borehole.
 2. A method as recited in claim 1 including displaying also said parameter of rotary torque and said parameter of penetration rate.
 3. A method as recited in claim 2 iNcluding plotting on a chart said ratio parameter psi .
 4. A method as recited in claim 3 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.
 5. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising: measuring parameters of rotary torque in said drill string and penetration rate of said drill bit through said earth formations when drilling a borehole; and obtaining the ratio parameter psi of said parameter of rotary torque divided by said parameter of penetration rate.
 6. A method as recited in claim 5 including plotting on a chart said ratio parameter psi .
 7. A method as recited in claim 6 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate. 